Feeding mechanism for arc lamps



Aug.125, 1936. F. c, COATES FEEDING MECHANISM FOR ARC LAMPS Filed June 13, 1934 5 5" m. w 3 Q 7 V ln'uenmr 6. M

Allomey:

Patented Aug. 25, 1936 UNITED STATES PATENT OFFICE 2,051,824 FEEDING MECHANISM FOR ARC LAMPS Application June 13, 1934, Serial No. 730,457

2 Claims.

This invention relates to carbon feeding mechanisms for electric arc lamps, and is particularly useful in arc lamps of the type employed in motion picture projectors, spot lamps, and the like, although it is also applicable to other types of arc lamps.

A broad object of the invention is to simplify the operation of striking the arc in an arc lamp.

Another object of the invention is to provide a simple, rugged mechanism capable of feeding the arc carbons together at a slow, constant rate to maintain the arc of constant length as the carbons are consumed, while providing for rapid movement of one carbon into and out of contact with the other carbon to strike the are.

A feature of the invention is a carbon-feeding wheel in frictional engagement with the carbon and having secured thereto for rotation therewith a Worm wheel meshing with an elongated worm which is mounted for either rotary or longitudinal motion so that the carbon may be moved slowly and accurately by rotating the worm, or may be reciprocated rapidly through a substantial distance (to strike the arc) by reciprocating the worm, the worm and worm wheel functioning as a rack and pinion in the latter movement.

The exact construction of an actual arc mechanism incorporating the invention, will now be described with reference to the drawing, in which Figure 1 is a side elevation view of an arc mechanism in accordance with the invention, certain parts being broken away and others shown in section; and

Figure 2 is a rear plane 11-11 of Fig. 1.

The mechanism disclosed comprises a frame member I mounted for longitudinal sliding movement on a pair of supporting bars 2, the ends of these bars being in turn supported from their ends in the usual manner (not shown in the drawing). The framework I has insulatingly supported therefrom a negative carbon support 3 and a positive carbon support 4. Thus the negative carbon support comprises a standard 5 inelevation taken from the sulatingly supported from the frame I by cap screws 6 which thread into the base of the standard 5. The standard is maintained out of electrical contact with the frame I by a gasket 1 of insulating material inserted therebetween and by washers 8 of insulating material positioned between the heads of the cap screws 6 and the underside web 9 of the frame I through which they pass. The holes in the web 9, through which the cap screws 6 pass, are of substantially larger diameter than the cap screws so that there is no electrical contact therebetween.

The standard 5 is bent at its upper end to support a heat-shield Ill, having an aperture therein through which the negative carbon II extends. Journaled in a web I2 of the standard 5, bank of the shield I0, is a carbon-feed roller I3 having a grooved face to contact with the carbon II. A pressure roller I4, also having a grooved face, is positioned opposite the feed roller I3, and serves to press the carbon firmly into engagement with the roller I3. Thus the pressure roller I4 is mounted on a lever I5 which is fulcrumed by a pin I6 to the web I2 and is constantly deflected in a direction to force the roller I4 toward the roller I3 by springs I 1 positioned between the lower end of the lever I5 and an extension I8 on the web I2 of standard 5.

The carbon I I is fed longitudinally by rotating the feeding-wheel I3 and the latter is rotated through a worm wheel I9 attached thereto and a cooperating worm 20. The worm 20 is secured to and supported by a shaft 2I which extends through and is Journaled in the standard 5 and is connected through an insulating joint 22 at its rear end to the forward end of a shaft 23. Shaft 23 extends rearwardly through a sleeve 24 and thence through a rear standard 25 in the frame I, terminating slightly beyond the standard 5. The rear end of shaft 23 is provided with a tongue 23a which engages with a groove in the forward end of a control shaft 26 which extends a substantial distance rearwardly of the main frame and terminates in a knob 21. The shaft 26 is supported in concentric relation with respect to the shaft 23 by a sleeve 28 which is secured by a bracket 29 to the standard 25. At its rear end the sleeve 28 is provided with a cap 30 for limiting rearward motion of the shaft 26 with respect to the sleeve 28. Thus it will be observed that the extreme left end of shaft 26 is of smaller diameter and that the orifice of the cap 30 is dimensioned to snugly engage this portion of smaller diameter so that in the position shown the shoulder at the juncture of the reduced portion of the rod with the main body of the rod abuts against the cap 30.

It will be observed from the description of the mechanism so far that by rotating the knob 21 the shafts 26, 23, and 2I, and Worm 20, will be rotated, the worm 20 in turn rotating the worm wheel I9 and the feed wheel I3 to shift the carbon II longitudinally in a direction depending upon the direction of rotation of knob 27. During this operation, the shaft 2I is prevented from moving longitudinally by a shoulder 3I on the left end of the worm 20, and a spring 32 surrounding the shaft 2|, and compressed between the standard 5 through which the shaft passes, and a collar 33 on the shaft immediately in front of the insulating joint 22. The shoulder 3I prevents any movement of shaft 2I to the left and the spring 32 has sufficient tension to prevent the reaction on the worm by the worm wheel I9 from displacing the shaft 2| to the right.

The spring 32, however, permits longitudinal movement to the right of the worm wheel 20, shaft 2!, shaft 23 and shaft 26, when sufficient force is exerted on the knob 21, and this movement is utilized to strike the arc. 7

Thus it will be observed that by pressingin on the knob Z'i and shifting the worm 20 to the right the worm and rack and pinion to cause relatively rapid rotation of the worm wheel l9 and the feeding wheel l3, and corresponding rapid longitudinal movement of the negative carbon ll into contact with the positive carbon 35. Thereafter, by releasing the knob 27, the worm 29 will be immediately retracted to the left by the spring 32, thereby rotating the feeding wheel H3 in the opposite direction and retracting the carbon I I into normal position away from the carbon 35, thereby striking the are. 7

Positive carbon 35 is supported in a manner. very similar to that described in connection with the negative carbon H. The carbon 35 extends rearwardly through a heat shield 36 supported on a standard 31 which is insulatingly supported on the frame I by cap screws 38 in cooperation with an insulating gasket 39 and an insulating washer 4i). 7 A feeding wheel 41 and a pressure wheel 42, which engage the positive carbon 35, are supported from the standard 31. Thus the pressure wheel 42 is supported on the forward end of a lever d3 fulcrumed to the standard 3'! by a pin a l and a spring 45 is provided to bear against the rear end of the lever 43 and compress the carbon 35 between the feeding wheels 4! and 42.

The feeding wheel 4!, which is journaled in the standard 3?, has attached thereto a worm wheel 56 which meshes with a worm 41 secured to a shaft 58 which is journaled in the standard 31. The rear end of the shaft 48 is secured by an insulating joint 49 to the forward end of a shaft 5a which extends rearwardly through, and is journaled in,'the standard 25 and is provided with an extension 5! upon the rear end of which is mounted a controlling knob am. By rotating the knob iila the worm 41 may be rotated to turn the worm wheel G8 and feeding wheel M to shift the positive carbon '35 longitudinally in either direction. It is unnecessary to provide, in connection with the positive carbon-feeding mechanism, a mechanism for rapid shifting of the carbon for the reason that in striking the are it is only necessary to shift the negative carbon.

Electrical connection is made to the two carbons H and 35, respectively, through the insulatingly supported standards 5 and 3'! upon which they are mounted. Thus a wire 52 may be clamped under the cap screw 6 for making electrical connection through the cap screw to the standard 5, and a wire 53 may be clamped under the cap screw 38 for making electrical connection to the'standard 37. The wires 52 and 53 are shown broken off in the drawingto simplify the latter, but it is understood that they may be extended to any suitable source of are current either directly, or, preferably, by extending the wires 52 and 53, respectively, first to a pair of binding posts 5 and 54a on the rear end of the frame I, which binding posts may be, in turn, connected to suitable leads extending to the source of current.

The mechanism so far described provides only for manual adjustment of the arc carbons. 'However, it' is desirable to provide automatic means for feeding the carbons at a uniform rate durworm wheel function as a.

ing normal operation. To this end, I have shown in the drawing a feed mechanism comprising an electric motor 55, which drives, through a suitable gear-train contained in a housing 56, a shaft 51 having a pair of Worms 58 and 59 thereon, which mesh with a pair of worm wheels i353 and 61, respectively. The worm wheel 89 is loosely mounted for rotation upon the sleeve 24 surrounding the shaft 23 and is compressed against a collar 62 on sleeve 25 by a spring 63 positioned between the left side of the worm wheel 68 and a nut 64 on the left end of sleeve 24. This mechanism constitutes a friction clutch between the worm wheel 69 and the sleeve 24. Sleeve 24 is in turn coupled with the shaft 23 to rotate the latter by a pin 64 on shaft 23, which engages with a longitudinal slot 65 in the sleeve 24. This slot 65 permits the longitudinal movement of the shaft 23 (during the operation of striking the arc) independently of sleeve 24, while forcing the two to always rotate in unison.

The worm wheel 6! is rotatably mounted upon the shaft 58 and is maintained in frictional engagement therewith by a spring 66 which is compressed between the wheel 6! and a nut 61, and forces the worm wheel against a collar 68 secured to the shaft 50.

With the construction described, whenever the motor 55 is set into operation, the worm wheels so and 6! are rotated at a uniform rate and cause the rotation of the worms 20 and 41, respectively, to feed the carbons at a predetermined desired rate. However, should the operator at any time desire to change the adjustment of either carbon, he may do so by merely grasping the knob 21, or am, associated with that carbon, and rotate it, the friction clutch mechanisms described permitting rotation of either the sleeve 24 or the shaft 5% without corresponding rotation of the associated worm wheels or 6|, respectively.

I claim:

1. In anarc lamp, means for supporting and feeding an arc carbon, a worm wheel, means connecting said worm wheel in driving relation to said carbon-feeding means for shifting the carbon in response to rotation of the worm wheel, a worm meshing with said worm wheel for driving the worm wheel, a shaft secured to and supporting said worm, means supporting said shaft for rotary and longitudinal movementwhile maintaining said worm in mesh with said worm wheel, a sleeve surrounding said shaft,'means for preventing longitudinal motion of said sleeve, means for rotating said sleeve, means slidahly coupling said sleeve to said shaft for rotation in unison therewith while permitting longitudinal -lll0V6- ment of said shaft independently of said sleeve, and means for shifting said shaft longitudinally.

2. In an arc lamp, means for supporting and feeding an arc carbon, a rotatably mounted shaft, gear means coupling said shaft to said feeding means for shifting the carbon in response to rotation of the shaft, manually actuated means for rotating said shaft, and power means for automatically yieldably rotating said shaft comprising a wheel loosely mounted on said shaft, a collar on said shaft against which said wheel abuts,

second collar on said shaft on the opposite side of and spaced from said wheel, spring means between said second collar and said wheel for resiliently urging said wheel into frictional engagement with said collar, and driving means geared to said wheel for rotating said wheel at auniform rate.

FIELDING o. COATES. 

